This invention relates generally to fluid dispensing systems, including multi-component fluid spraying and pouring systems, and, more particularly, to the fluid supply apparatus, plural component valves and dispensers and sprayers of such systems.
Multi-component fluid dispensing systems are used in many manufacturing applications. For example, multi-component spraying systems have been used in manufacturing plastic articles by applying resinous materials to a mold or a preform for the article. In such systems, a liquid resin and a catalyst for the resin are formed into spray particles directed to a substrate where the catalyst and resin react and harden to form the articles. In such applications, two components, for example a resin and a catalyst, are preferably mixed together and the mixture is sprayed onto the substrate.
Multi-component fluid dispensing systems have also been used, for example, in the manufacture of insulating foams. In such systems, a first component and a second component, for example, a polyol resin and an isocyanate, are mixed and after mixing dispensed or sprayed into or onto an article of manufacture where the mixed components react to produce a hardened insulating foam.
More recently, multi-component painting systems have been developed that apply plural fluid components that react, when mixed, to form hardened, decorative and protective coatings, and other applications for multi-component dispensing systems are continuing to arise with the development of new plural component materials.
Multi-component dispensing systems for mixed plural component materials are divided generally into two categories, those in which the multiple components are mixed externally to the system apparatus (referred to as external mix systems) and those in which the multiple components are mixed within the system apparatus (referred to as internal mix systems). In both external mix and internal mix systems, it is important that the components be supplied for mixing at the precise ratios recommended by the plural component material manufacturers for curing the mixed plural component material. The effective use of plural component material requires fluid dispensing systems that may be adjusted to vary widely the ratios between the fluid components of the plural component material; for example, multi-component fluid dispensing systems must be capable of mixing and dispensing materials with ratios from 1:1 to as high as about 16:1. If, in operation, a fluid dispensing system varies the precise ratio or generates pressure imbalances within the system, it may dispense fluid materials that result in partially cured or uncured portions as a result of departure from the required mixing ratios and unsatisfactory mixing.
Such variations in the operation of a fluid dispensing system can be particularly harmful in internal mix systems where the components are mixed within the fluid dispensing device. It is common in such internal mix dispensing systems that the fluid dispenser include an internal mixing chamber into which the plural components to be mixed are injected by the multi-component fluid delivery system, as shown, for example, in spraying dispensers of U.S. Pat. Nos. 3,240,432; 3,366,337; 3,379,376; 3,790,030; 3,799,403; and 4,123,007. Various agencies are used to clean the internal mixing chamber in internal mix dispensers. For pour type dispensers, the internal mix chamber is frequently purged of mixed plural component material by a rod which is thrust through the mixing chamber, or by solvent which is forced to flow through the mixing chamber. In spray-type dispensers, the internal mixing chamber is frequently purged of mixed plural component material by either a flow of compressed air or solvent or occasionally both.
Multi-component dispensers frequently also include diametrically opposed orifices for the injection of the plural components into the mixing chamber to assist in mixing as shown, for example, in U.S. Pat. Nos. 3,366,337; 3,790,030; and 3,799,403. In such systems, particularly those with diametrically opposed injection orifices, transient pressure and flow imbalances can not only result in the dispensing of off-ratio material which may not properly cure, but the injection of one component into the dispenser passageways of the other component where it can mix with the other component out of reach of the cleansing agent and cure to form a blockage in the dispenser or a flow restriction that with throw the system off-ratio.
The fluid dispenser of the multi-component dispensing system is generally supplied with the plural components by a multi-component fluid delivery system which maintains the components separate and apart from each other until they are mixed. The multi-component fluid delivery systems include first and second supply tanks for storing supplies of the components to be mixed. Frequently, a transfer pump is connected to the output of each tank to transfer components to proportioning pumps which, in turn, are provided to deliver each component to the dispenser of the system at the precise desired rate.
Compressed air is generally available in manufacturing facilities for the operation of various power-driven hand tools that are frequently used in manufacturing operations. It is convenient and desirable that the fluid dispensing system be adapted to operate from such compressed air, which is frequently referred to as "factory air". Thus, fluid delivery systems frequently include a control which is connected with the factory air, and flows of compressed air are directed and controlled by the fluid dispensing system control to operate and control the valves and pumps of the fluid dispensing system.
In most systems, the proportioning pumps generally comprise positive displacement pumps, most frequently reciprocating piston pumps, which are driven from a single air motor by a common interconnecting mechanism in a proportioning pump assembly. The proportioning pump assembly permits each of the positive displacement pumps to be mounted between an assembly base and the common mechanism in a variety of positions that provide variations in the ratio of the components as each of the component pumps is operated by the air motor through the common interconnecting mechanism. By varying the mechanical interconnection of each component pump between the base and the common interconnecting mechanism that drives the pump, with each stroke of the air pump, each reciprocating piston of each proportioning pump can be driven through a different stroke length and deliver a different flow volume of each component.
The fluid dispensing system control can include a motor air control valve that is connected between the source of factory air and the air motor of the fluid dispensing system and is operable to control the flow of air to the air motor and thereby the operation of the positive displacement component pumps of the fluid delivery system. The fluid dispensing system control can also include, for example, a leak relay which controls the application of air pressure from the factory air source to the motor air control valve for operation of the motor air control valve and the air motor. Such a leak relay can be connected to the factory air source and through a flexible fluid hose with a small air valve on the dispenser so that by operation of the air valve by the system operator through actuation of a trigger, button, lever or other such mechanical actuator, a flow of air is established from the factory air source through the leak relay, which will operate the motor air control valve and thereby operate the air motor and component pumps. The trigger, button, lever or mechanical actuator of the dispenser can also simultaneously operate a fluid valve or valves controlling the flow of the plural components through the dispenser for application by the system operator. Fluid dispensing systems frequently include an air driven actuator on the dispenser for operation of the component flow control valves carried by the dispenser.
In existing systems, the fluid dispenser control, once the system is placed in operation, operates the motor air control valve to apply air pressure to the air motor at all times and controls the dispensing of fluid material by fluid flow control valves carried by the dispenser and operated by the system operator. In such existing systems, when the system operator wants to dispense material, he opens the fluid flow control valves carried by the dispenser to permit each of the plural components to flow into and through the dispenser. In internal mix systems, the fluid flow control valves of each of the components are upstream of the internal mixer. When these valves are closed, to stop the dispensing of fluid material, the fluid pressure within the conduits leading from the fluid component pumps to the fluid valves increases as a result of the increased static pressure applied to the air motor of the fluid dispensing system, which is greater than the operating air pressure of the air motor, which is reduced as a result of the various pressure drops due to air flow restrictions in dispensing system control and, to some extent, the factory air distribution system.
When the system operator thereafter opens the fluid component flow control valves of the dispenser, the higher fluid pressure resulting from the increased static air pressure applied to the air motor, results in momentarily increased fluid pressure and flow rates of the plural component materials into and through the fluid dispenser which results in transient flow rates in excess of the desired flow rate and the dispensation of mixed plural component materials which are off-ratio. In addition, the transient pressure and flow increases, particularly where the components of the system were mixed with high ratios, one to the other, for example, in the range of 8:1 to 15:1, interfere with proper mixing of the components and, because of the wide pressure imbalance, can frequently force one-component material into passageways of the other component material within the dispenser which cannot be purged by the cleansing agent.
In some systems, the fluid delivery systems include heat exchangers and heated hoses to heat and maintain the temperature of the components of a plural component material prior to delivery of the dispenser. In addition, some fluid delivery systems include components permitting the recirculation of the plural component materials, whether heated or unheated, between the dispenser and their sources. An example of such systems is disclosed in U.S. Pat. No. 4,809,909.